Apparatus for loading bagged mail from a loading dock into a highway vehicle



0ct. 28 1969 J. E.- MCWYILLIAMS APPARATUS FOR LOADING BAGGED MAIL FROM A LOADING. DOCK INTO A HIGHWAY VEHICLE Filed April 4, 1968 2 Sheets-Sheet 1 N mf L m #u l INVENTOR JOSEPH E M WILL I AMS BY %4um ATTORNEYS Oct. 28. 1969 J M WILLIAMS 3,474,915 APPARATUS FOR LOADING BAGGED MAIL FROM A LOADING DOCK INTO A HIGHWAY VEHICLE Filed April 4, 1968 2 Sheets-Sheet 2 289 272 INVENTOR JOSEPH E. MQWILLIAMS 286 FIG-.5

AT TO R NEYS United States Patent US. Cl. 214-6 6 Claims ABSTRACT OF THE DISCLOSURE The invention relates to the loading of mail bags from a loading dock into an end loading highway vehicle, such as a truck or a trailer, to fully load the vehicle with stacks of mail bags in which the bags are compactly loaded into place in individual stack forming tiers without those performing the bag loading operation having to enter the vehicle. In practicing the invention, the loading dock at the post oflice or the like is provided with a conveyor on which out-going bags are placed and oriented in closely spaced tier form to form a stack forming tier unit. Operating between the conveyor and the highway vehicle is a carriage, in the form of a carrier riding on trackways formed on a cantilevered open centered support frame mounted on the dock, with the dock supported frame being so positioned and proportioned that it projects into the vehicle substantially up to the forward end of its loading area when the vehicle is backed into loading position adjacent the dock. The carrier receives the tier load Without disturbing the orientation of the bags and brings the tier load into the vehicle loading area for discharge of the stack forming tier unit, and effects placement of the tier as part of a stack in the vehicle, again without disturbing the orientation of the bags. The carriage then returns to the conveyor for another tier load.

The carriage movements are controlled longitudinally and vertically of the highway vehicle so that the individual tier loads are formed into vertical stacks of mail bags that are disposed to position the bags of adjacent stacks in closely spaced relation with the vehicle being thus filled with bags throughout its load receiving area so as to make maximum use of the available loading space within the vehicle to maximize the pay load. The operation of the carriage is fully mechanized so that workers do not have to go into the vehicle, and palleting of the bags in groups is avoided while still achieving uniform loading in tier form.

This application is closely related to my application 1 Ser. No. 694,151, filed Dec. 28, 1967.

This invention relates to a method and apparatus for loading bagged mail from a loading dock into a highway vehicle, and more particularly, to methods of and means for facilitating the handling of bagged mail in individual load groups for purposes of loading same into vehicles that are to transport it.

Conventional methods of loading mail bags into highway vehicles and trailers of the end loading type are not only time consuming and ineflicient in nature, but also require much manual effort on the part of the workers involved. The bags are conventionally loaded so as to form vertical stacks in which the bags of each stack extend longitudinally of the vehicle and the stacks fill all available space vertically and lengthwise of the vehicle. The bags, which when loaded are from 12-14 inches wide and 36-40 inches long, are usually loaded up to about 92 inches above the floor of the truck in a space that is about eight feet wide, with the length depending on the length of the truck.

ICC

Heretofore the loading procedures have been largely manual in nature, with the workers involved dragging the individual bags into the vehicle from a pile of the bags on the adjacent loading dock, and then individually positioning and lifting the bag as is necessary to complete the formation of the respective bag stacks. At best, hand carts are sometimes employed to reduce some of the manual effort involved, but the handling required of each individual bag is still much the same; in both cases, much repetition of bag orienting movements is required for each bag, which is wasteful of effort and inefficient in terms of the time and cost of getting the job done. The result is that valuable equipment is unduly tied up to accommodate these slow loading procedures, and labor is in short supply as workers are becoming increasingly reluctant to take on jobs involving such hard work.

Nevertheless, the Post Office Department and others concerned with the transport of loaded mail bags, load something on the order of 50,000 trucks a day in the U.S.A. in this manner at a cost on the order of $18 a truck, which gives an indication of the magnitude of the problem.

My Patent 3,164,271, granted Jan. 5, 1965, discloses a basic system for handling bagged mail which involves the sorting and loading of incoming bags into tier load units that are grouped by destination and stored until arrival of a suitable load transport vehicle whereupon the tier load units are unloaded in single or multiple tier form in the vehicle.

A principal objective achieved by the methods and apparatus disclosed in said patent is that the mail bags are oriented early in the cycle of their handling operations and this initial orientation is maintained throughout all of the subsequent handling operations.

The present application is directed to an additional embodiment of the basic arrangements shown in my said application.

A principal object of the present invention is to provide methods and apparatus for further facilitating the loading of end opening vehicles without requiring that the operator enter the transport vehicle or that the mail bags be palleted in groups to reduce individual handling.

Another principal object of this invention is to provide a method of loading bagged mail in transport vehicles in closely spaced relationship to the end that the available air spaced within the vehicle will be loaded to the maximum and all manual motions ordinarily required to handle the bags within the vehicle are performed by mechanical means arranged to carry, elevate as necessary and deposit the bags in the compact relationship necessary to maximize the pay load by substantially filling the available cubic loading space of the vehicle.

Another principal object of the invention is to provide methods and apparatus for loading of end opening vehicles such as motor trucks and trailers which permits a single operator to efiiciently load the entire transport vehicle without stepping inside it.

Still other objects of the invention are to provide apparatus for loading bagged mail in transport vehicles that is adapted for full push button type actuation and control, to provide methods and apparatus for handling bagged mail that permits substantially automatic handling of the mail in tiered or other types of load unit groups, and to provide mail bag handling apparatus that is economical of manufacture, convenient in use, and adapted for all conventional mail bag loading dock areas and vehicles or their equivalents.

Other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings.

In the drawings:

FIGURE 1 is a diagrammatic side elevational view of a semi-trailer in the process of being loaded in accordance with my present invention, with the semi-trailer shown in section, and the mail bag load unit carrying carriage being shown in its load receiving position in the right hand dashed line position while its full line positon shows one of the load discharging positions thereof;

FIGURE 2 is a plan view of the apparatus shown in FIGURE 1;

FIGURE 3 is a fragmental cross-sectional view taken substantially along line 33 of FIGURE 1;

FIGURE 4 is a plan view of the load unit carrying carrier that is shown in FIGURE 3; and

FIGURE 5 is a fragmental side elevational view of the mid portion of the carrier as shown in FIGURE 1.

However, it is to be distinctly understood that the specific embodiment of the invention illustrated is supplied primarily to comply with the requirements of the Patent Code, and that the invention may have other embodiments.

GENERAL DESCRIPTION Reference numeral of FIGURE 1 generally indicates one embodiment of the present invention that incorporates the basic approach of my said application Ser. No. 694,217 for loading mail bags from a loading dock 12 into an end loading vehicle 14, which has been illustrated as being in the form of the familiar semitrailer, although the invention is readily applicable to any end loading vehicle.

It is assumed that the mail bag handling installation involved includes the loading dock 12 (of a post office or the like) that is conventionally provided with a level load support surface 16 and the usual shoulder or end 18 adjacent to which the vehicle 14 is backed up for purposes of being loaded.

It is also assumed that the vehicle 14 be in the form of the usual body 20 defined by forward end wall 22, top wall 24, side walls 26 and 28, floor 30, and end opening 32 that is customarily closed by suitable doors or the like (not shown). The body 20, being of the semi-trailer type, rides on the usual rear wheels 34 and is provided with the usual kingpin 36 for connection to the fifth wheel of a conventional tractor truck (not shown).

In accordance with this invention, there is associated with the loading dock 12 at the position 36 where the vehicle body 14 is to be stationed for loading purposes a mail bag receiving conveyor 38 and a mail bag tier conveying carriage 40, which receives the mail bags accumulated in tier form or conveyor 38, transports them into the vehicle 14 and discharges them in tier form to form mail bag stacks 42.

Under ordinary circumstances, the loading clock 12 is located at a post ofiice or the like where loaded mail bags are processed for shipment to their destinations, and as indicated in FIGURE 2, the conveyor 38 and the carriage 40 are longitudinally aligned with the vehicle 14 (in the loading position of the vehicle) and have a width transversely thereof to accommodate enough mail bags 44 laid side by side in a row to form one complete tier 46 of a stack 42, such that when the tier is placed within the vehicle 14, it will extend substantially from one side wall 26 to the other side wall 28 as indicated in FIGURE 2. Conveyor 38 is in the form of conveyor belt 39 defining an upwardly facing load supporting surface 41 on which the bags 44 are placed, which surface, at least at the lower, loadingend 38A of conveyor 38, is at an easy reach height above surface 16, such as two to three feet high.

The carriage 40 comprises a load support in the form of a carrier 126 riding in trackways 120 defined by the vertically movable open centered, generally I-I-shaped, frame 124 mounted on a hydraulic jack device 125 with which loading dock 12 is equipped. Carrier 126 is positioned between cables 128 mounted on either side of the frame 124 in the form of appropriately tensioned closed loops and trained over suitable end pulleys and 132. Pulleys 130 and 132 are respectively journaled on frame 124 which is raised and lowered by operation of jack device 125 under control of control mechanism 133 which is associated with loading dock 12 in any suitable manner. The carrier 126 is fixed to the respective cables 128 at brackets 127 and the cables 128 are powered by a suitable drive mechanism 137 to cycle the carriage 40 forwardly and rearwardly of the frame 124 and thus of the vehicle 14 when it is in loading position. The carrier 126 of FIG- URES 1-6 forming the carriage 40 is formed with a retractable shelf or slide plate 139 on which a mail bag tier 46 is placed by operating the conveyor 38, and when the carrier 126 is positioned to dispose the tier of bags over the spot they are to be dropped into in accordance with this invention, the shelf 139 is drawn to the discharging position shown in dashed lines in FIGURE 2 by pulling on cables 140 through suitable mechanism 141 under the control of the operator (without moving the carriage 40 rearwardly of the vehicle).

The conveyor 38 is in the form of a frame 202 including side members 204 and 206 between which are journaled the rollers 208 that support belt conveyor 39. Frame 202 is pivotally supported on frame 124 as at 122, and at its lower end rides on rollers 123 as the forward end of frame 124 is adjusted vertically.

In practicing my invention, the mail bags are brought in any suitable manner to the area of the conveyor 38 and they may be piled at random adjacent the conveyor 38 for ready access by one or more workers stationed adjacent the conveyor 38 for purposes of controlling the operation of same and carriage 40. In accordance with this invention, the controls for conveyor 38 and carriage 40 are arranged so that these pieces of apparatus are operated without anyone having to go into the vehicle 14, as will be hereinafter described in connection with the embodiment of the invention illustrated in the drawings. For this purpose, the controls may be of the push button type applied to suitable control panel 35 and may be of any suitable electric and/or electronic type that will serve the purpose.

To practice my invention, after the vehicle 14 is positioned as shown in FIGURES 1 and 2 for loading (assuming it is empty), and the bags to be shipped are disposed, for instance in a pile or piles adjacent the conveyor 38, the worker or workers in the area of conveyor 38 pick up and position enough of the individual bags 44 to form one or more tiers 46 (of six to eight bags in a tier) on the belt 39 of conveyor 38 in which, in accordance with the procedure contemplated by this embodiment of the invention, the bags of each tier 46 are placed in closely spaced side by side relation and extend longitudinally of the conveyor 38 and vehicle 14. Assuming the vehicle 14- is empty, frame 124 is lowered to the lowermost position shown in FIGURE 1 to dispose carrier 126 so that bags 44 dropping therefrom will drop no more than 24 inches to the floor 30.

When one or more tiers 46 have been applied to conveyor 38 in the manner indicated (which tiers are termed a partial transport vehicle load depth unit in the appended claims), the carriage 40 is positioned in load receiving relation to conveyor 38 and conveyor 38 is actuated to deposit simultaneously all the bags 44 forming the first tier 46 on the carrier 126, its shelf 139 being disposed in its load supporting retracted position of FIG- URE 4. It will be noted that the rear end 52 of the carrier 126 will need to be disposed to present the shelf 139 (as positioned in FIGURE 4) in load receiving relation with respect to the forward end 54 of the conveyor 38 when carrier 126 is in its load receiving position of FIG- URE 1, such that when the bags drop from end 54 of conveyor 38, they will assume the positions on shelf 139 that are indicated in FIGURES 1 and 2.

The carriage 40 is then actuated to move same from its loading position into the vehicle 14 where it moves toward the front wall 22 of the vehicle to start the first stack 42 of mail bags. The carriage 40 moves forwardly of the vehicle 14 until a suitable limit switch arrangement such as that indicated at 56 at its forward end 50 engages the vehicle forward wall to stop the forward movement of the carriage 40 and actuate mechanism 141 to move shelf 139 to its bag discharging position, whereupon the first tier of bags is dropped onto the floor 30 of the vehicle adjacent the end wall 22 in the position indicated at 58.

The carriage 40 is then returned to its loading posi tion to receive the next tier 46 of mail bags 44, which can be formed on to the conveyor 38 while the carriage 40 is operating in the manner that has just been described. Shelf 139 is either returned by hand to its load supporting position as carriage 40 returns to its load receiving position or by engagement with suitable stops 138 of frame 124 as the carrier 126 is moved rearwardly to full load receiving position, mechanism 141 operating automatically to wind up the slack in cables 140. The next tier is then transferred to carrige 40 in the manner already suggested. This next tier, in accordance with one manner of pnacticing my invention is then unloaded in the manner already described, but adjacent the first tier unloaded, Where indicated at 60, the carrier 126 being automatically stopped at the position required to do this by appropriate sequence controls built into the circuiting controlled at panel 35.

The next tiers are similarly handled to form a horizontally disposed layer 113 of tiers 46, along the floor 30 of vehicle body 14 back to the vehicle open end 32. In doing this, the carriage 40 is maintained at its initial elevation above the floor 30 of vehicle body 14 until the first bag layer 113 is fully in place between forward wall 22 and door opening 32, after which the frame 124 is raised, by operating mechanism 133, into a position suitable for forming the next layer 113, which is formed in the manner described for the first layer 113. This is repeated until the vehicle is filled, after which the vehicle open end is secured in the usual manner and the vehicle 14 driven off to be replaced by a similar vehicle 14 that is loaded in like manner.

The handling of the bags in moving them from the conveyor 38 to their respective positions in the vehicle 14 is thus carried out after having made a single orientation of the bag as to the position it is to take in a particular stack forming tier, and without having to drop the bag over the 24 inch limitation provided for by the Post Office regulations.

From the description so far there are several important features to be observed. Note for one thing that the bags 44 are properly oriented in their tier 46 by their application to the conveyor 38, and that this orientation is maintained throughout the further handling of the bags that moves them into stacked relation in the vehicle 14. Furthermore, the lifting and positioning of the bags 44 onto conveyor 38 is the only manual labor involved, and the workers is concerned with only as easy lifting and positioning action at a convenient working height above surface 16, with such action needing only to be performed once per bag.

It is also to be noted that the loading of the vehicle 14 is done without anyone having to enter the vehicle 14, and-palletizing of the individual tier 14 is unnecessary.

SPECIFIC DESCRIPTION The carrier 126 comprises a frame 284 including side plates 286 and a transverse bag stop plate 289 fixed together in any suitable manner to defiine an essentially open centered frame configuration as well as a slideway 285 for the slide plate 139 that is pulled from the solid line load supporting position of FIGURE 1 to the dashed line position of that figure to discharge the mail bag tier 46 that is carried thereby onto the vehicle floor 30 or mail bag stack on which it is to be placed. Side plates 286 are angled inwardly as at 270 to support plate 139, and stop plate 289 extends short of slideway 285, as at 272.

The carrier side plates 286 on the outwardly facing sides thereof each journal a pair of rollers 290 that ride on the trackways 120 of frame 124. Cables 128, to which carrier 126 is fixed in any suitable manner at lugs 127, has their respective ends closed together to form the indicated closed loop 293 about the respective pairs of pulleys 130 and 132 in any suitable manner.

The frame 124 comprises a pair of elongate tapering frame members 300 of channel-shaped cross-sectional configuration (see FIGURE 3) of which the lower flange 301 is horizontally disposed and defines the respective trackways 120. Frame members 300 are joined together by suitable brace plates 302 and 304, with the lower brace plate 304 being secured to jack device 125. The space 303 separating members 300 between their forward ends 305 and plates 302 and 304 is continuous and uninterrupted to accommodate discharge of the mail bags from carrier 126 at the various positions required to fully load vehicle 14.

At their rear ends 306 frame members 300 are joined together by plate 307 on which is mounted motor 308 that comprises drive mechanism 137, which motor 308 reversibly drives cables 128 through shafts 309, sprockets 310 and 312, and chains 311 connecting the respective sprockets 310 and 312, sprockets 312 and pulleys 132 being keyed to the same shaft 313 that is journaled in the respective frame members 300.

Conveyor 38 is in the form of a frame 202 including the side members 204 and 206 in which are journaled the rollers 208 that support the belt conveyor 39. Belt conveyor 39 is driven by a suitable electric motor 205 supported on a suitable bracket plate 207 carried by frame 202 adjacent the conveyor rearward end pulley and driving same through a pulley belt or the like (not shown). The pivotal connection 122 between frame 202 and frame members 300 may be of any suitable type.

The frame 202 of conveyor 38 and frame 124 are so proportioned that side plates 286 of carrier 126 fit between them in the loading position of carrier 126 (see dashed line position of FIGURE 1). Conveyor 38 is made of sufiicient length so that in any operative position of conveyor 38 that is achieved by vertical positioning of frame 124 to fill vehicle 14, the bags dropping off the forward end of conveyor 38 onto carrier 126 will drop no more than the 24 inches permitted by Post Oifice regulations.

Frame 124 also includes mounting plate 325 spanning the space between the frame members 300 on which is mounted motor 329 (comprising mechanism 141) which operates shaft 331, journaled on plate 325 and having reels 333 keyed thereto to which cables .140 are respectively attached for pulling cables 140 (under the action of motor 329) to retract the slide plate or shelf 139 when unloading of the mail bags from the carriage 40 is desired, with the drive for the latter motor being arranged so that ca-bles 140 pull out readily firom their reels (without displacing shelf 139) when the carriage 40 is moved toward the desired bag tier load discharging position. This may be done in any suitable manner. Cables 140 are suitably anchored to angle brackets 337 applied to slide plate or shelf 139 as at 327. The stops 138 are fixed to plate 135 to project above the plane of operation of shelf 139. Plate 325 is notched as at 335 to accommodate reels 333.

Jack device comprises hydraulic cylinder 340 that is mounted in dock 12 in any suitable manner, which includes piston member 342 that is fixed to plate 304 of frame 124 in any suitable manner. Mechanism 133, which is illustrated in largely block diagram form, includes a suitable motor, pump, source of hydraulic liquid,

conduiting, and the like to raise frame 124 by supplying hydraulic liquids to the lower end of cylinder 340 through conduit 344, as may be necessary under the control of the operator at panel 35 to position frame 124 at the desired elevation to form the mail bags into the superposed horizontal rows 113 for the full loading height of the vehicle 14.

The operation and movements of the conveyor 38 and bag carrying carriage and parts thereof are preferably completely controlled from a control panel 35, or the like, located outside of the vehicle 14, through any suitable wiring arrangement that incorporates the various motors and switches that have been referred to, and ordinarily only a single operator will be needed to both load the bags on the dock supported conveyor 38 and operate the machines involved to deposit the bags in the vehicle 14. The machines involved can readily be controlled to avoid dropping the bags further than the 24 inch limitation prescribed by the Post Ofiice Department.

The conveyor 38 shown in the illustrated embodiment is considered an optional way of loading carrier 126. An alternate way of doing the same thing would be to eliminate conveyor 38 and mount on dock 12 adjacent the end of frame 124 a second frame that is vertically movable to position same at an appropriate load discharging elevation relative to carrier 126 (as by employing power unit 133), that is shaped for efficient load transfer of bags from same to carrier 126, and that includes a suitable powered pusher plate means of the type described in my said patent to effect discharge of a bag tier from same onto the carrier 126.

The bag stacking arrangement of this invention will load trucks and trailers in a fraction of the time now required and at less than half the cost, while at the same time greatly reducing the effort required by workers handling the bags. This not only greatly reduces the tie up time for each truck, but also significantly reduces the overall cost of mail bag handling.

As to all described embodiments and methods herein disclosed, the load units or tiers formed on the loading dock are termed partial transport vehicle load depth unit in the appended claims.

The foregoing description and the drawings are given merely to explain and illustrate my invention since those skilled in the art who have my disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

I claim:

1. In bulk mail handling apparatus for loading elongated mail bags from a loading dock into the load receiving area of an end loading transport vehicle backed into load receiving position adjacent the dock to dispose its end opening to receive the bags, without workers on the dock handling the bags having to enter the vehicle, and without requiring that pallets remain with the bags after they are loaded into the vehicle, said apparatus comprising:

a conveyor mounted on the loading dock adjacent the load receiving position of the vehicle and having a width transversely thereof approximately the width of the vehicle area,

said conveyor being positioned to be aligned with the vehicle and its end opening in the load receiving position of the vehicle,

said conveyor presenting an upwardly facing load transporting surface having at least a portion thereof at an elevation for convenient manual lifting of the bags from the dock onto the conveyor surface,

a vertically movable horizontally disposed frame mounted on the loading dock between said conveyor and said load receiving position of the vehicle and positioned to be aligned with said conveyor longitudinally thereof,

said frame defining a trackway proportioned to extend into the vehicle when same is in its said load receiving position and project substantially to the forward end of the load receiving area thereof,

a mail bag receiving carriage adapted to operate on said trackway between said conveyor and the forward end of said trackway and proportioned to enter said vehicle end opening,

means for moving said carriage longitudinally of said trackway,

said carriage including a load supporting surface approximately the Width of the vehicle area and in substantial horizontal alignment with said trackway,

means for adjusting vertically said frame for adjusting vertically said carriage load supporting surface,

and means for discharging from said carriage surface "bags received thereon from said conveyor, whereby mail bags may be loaded onto said conveyor surface with the bags thereof oriented to extend longitudinally of the vehicle and in side by side tier forming relation, and said tier of bags may be mechanically transferred between said conveyor surface and stack forming positions in said vehicle area while maintaining said orientation.

2. The apparatus set forth in claim 1 wherein:

said conveyor is pivotally connected to said frame adjacent the forward end of said conveyor to dispose said forward end of said conveyor over said tracky,

with the rearward end of said conveyor riding on roller means engaging the dock.

3. In bulk mail handling apparatus for loading elongated mail bags from a loading dock into the load receiving area of an end loading transport vehicle backed into load receiving position adjacent the dock to dispose its end opening to receive the bags, without workers on the dock handling the bags having to enter the vehicle, and without requiring that pallets remain with the bags after they are loaded into the vehicle, said apparatus comprising:

a conveyor mounted on the loading dock adjacent the load receiving position of the vehicle and having a width transversely thereof approximately the width of the vehicle area,

said conveyor being positioned to be aligned with the vehicle and its end opening in the load receiving position of the vehicle,

said conveyor presenting an upwardly facing load transporting surface having at least a portion thereof at an elevation for convenient manual lifting of the bags from the dock onto the conveyor surface,

a vertically movable horizontally disposed frame mounted on the loading dock between said conveyor and said load receiving position of the vehicle and positioned to be aligned with said conveyor longitudinally thereof,

said frame defining a trackway proportioned to extend into the vehicle when same is in its said load receiving position and to project substantially to the forward end of the load receiving area thereof,

a mail bag receiving carriage adapted to operate on said trackway between said conveyor and the forward end of said trackway and proportioned to enter said vehicle end opening,

said carriage being secured at either side thereof to a closed loop cable,

end pulley means carried by said frame over which said cables are trained,

said carriage including a load supporting surface approximating the width of the vehicle area and in substantial horizontal alignment with said trackway,

means for driving said cables for moving said carriage between a mail bag receiving position adjacent said conveyor and predetermined mail bag discharging positions within the vehicle,

means for adjusting vertically said frame for adjusting vertically said carriage load supporting surface,

and means for discharging from said carriage surface bags received thereon from said conveyor at predetermined stack forming positions in the vehicle load receiving area, whereby mail bags may be loaded onto said conveyor surface with the bags thereof oriented to extend longitudinally of the vehicle and in side by side tier forming relation, and said tier of bags may be mechanically transferred between said conveyor surface and stack forming positions in said vehicle area while maintaining said orientaton. 4. The apparatus set forth in claim 1 wherein: said means for vertically adjusting said frame comprises:

lift means carried by the loading dock, said frame being mounted on said lift means, and means for actuating said lift means to raise and lower said frame between predetermined load discharging positions of said carriage. 5. The apparatus set forth in claim 3 wherein: said conveyor comprises an endless conveyor carried adjacent the forward end thereof by said frame and being pivotally connected to said frame in load transmitting relation thereto and the other end thereof riding on the loading dock.

6. The apparatus set forth in claim 3 wherein:

said carriage load supporting surface comprises a shelf member mounted for movement between a mail bag tier load supporting position and a load discharging position,

and means for mechanically moving said shelf member between said positions.

References Cited UNITED STATES PATENTS 1,161,680 11/1915 Hulett 212-3 1,534,797 4/1925 McLeod q 21441 2,755,945 7/ 1956 Gilson.

3,381,828 5/1968 Sheehan.

GERALD M. FORLENZA, Primary Examiner 2 ROBERT J. SPAR, Assistant Examiner U.S. Cl. X.R. 

